Linear accelerator devices use intense radio frequency electromagnetic fields to accelerate the speed of particles to create beams used for a variety of applications. These applications include driving industrial processes, security & imaging applications, food and medical sterilization, medical treatments, isotope creation and physics research. SRF (Superconducting Radio Frequency) technology allows for the construction of linear accelerators that are both compact and efficient at using “wall plug” electrical power to create a particle beam.
SRF accelerating cavities are commonly used in linear accelerators or particle accelerators. Due to their very small RF losses, much higher acceleration efficiencies, and higher continuous wave (CW) accelerating fields than normal conducting cavities, SRF cavities are now considered the device of choice for many of today's leading applications in high energy and nuclear physics, including energy recovery linear accelerators (ERLs), linear colliders, neutrino factories, spallation neutron sources, and rare isotope accelerators. These projects place enormous demands not only on advances in beam performance, but also on more reliable and economic methods for fabrication, assembly, and operation.
Some SRF linear accelerators may employ the use of multicell cavities rather than simply a single cavity. Multicell cavities must meet certain requirements to operate properly in a particle accelerator in terms of resonance frequency, field flatness and eccentricity. Cavities are typically tuned to meet these requirements by plastic deformation. Tuning must be accomplished before welding a helium vessel to the bare cavity when there is access to the cavity's cells. Dressed cavities, however, can become detuned during the preparation, testing, and qualification process, which basically renders them unusable for the cryomodule assembly. Currently, a straightforward process does not exist for tuning dressed cavities other than cutting the helium vessel to access the outer surface of a cavity cell, then tune the bare cavity and dress it back. This typically has a significant impact on the cost and the schedule of large-scale particle accelerator projects, which can include, for example, hundreds of cavities.